Nokia Astound - Can I use the Navigation without my SIM card in my Nokia device?

Yes but service is limited to only those features that do not require network connection. (My current location based on GPS coverage). Maps can be used offline to avoid data charges, however the following options will not be available in Offline Mode:

View Satellite maps

View Terrain maps

Search the latest address/POI database

Real-time Traffic and Safety updates

Share your status, photos and location to your Facebook profile

Get Weather forecasts

Services listed under More menu

Synchronize your locations with Nokia Maps on the internet

You can switch between Online and Offline mode by going to the Maps Settings and select Internet > Connection > Online or Offline